THE ORIGIN OF THE WOLFRAM AND CASSITERITE ORES 329 



scopic crystals," and again, ' it is worthy of notice that no fiuor spar 

 was found anywhere." As far as we know tourmaline does not 

 exist in the wolfram-bearing veins of Tavoy, though it is found in 

 pegmatites of later date, while flourite has a wide distribution in 

 small quantities. We believe that this is the unanimous opinion 

 of all geologists who have examined the Tavoy field in recent years. 

 Curiously enough, tourmaline is a common vein mineral with wolfram 

 and cassiterite in the Amherst, Thaton and Mergui districts to the 

 north and south of Tavoy respectively. 



Bleeck believes that the veins were formed after the solidification 

 of the main granite mass, by mineral solutions which deposited 

 their load in fissures in the granite and the country rock. Following 

 the igneous effusion but before consolidation, local differentiation 

 is believed to have taken place, causing the heavy metals with some 

 mother liquor to separate from the quartz-felspar-mica magma. 

 The formation of separate cassiterite-quartz lodes distinct from 

 the wolfram lodes is held to be caused by the formation of numerous 

 distinct centres of differentiation. The responsibility of aqueous 

 solution for the formation of wolframite lodes is said to seem abund- 

 antly clear, if only from the one fact that the gangue quartz is 

 crammed with liquid inclusions. At the same time the pneuma- 

 tolytic process of mineral formation went on side by side with the 

 deposition of lode matter from solutions, for such a process " need 

 in no way clash either chemically or physically with the theory of 

 lode formation from magmatic injections or aqueous solutions." 

 Again, Bleeck believes that in some cases the mother liquor which 

 had become differentiated from the granite magma may have been 

 injected into the fissures in magmatic state and not in the form of 

 aqueous solutions. 



J. Coggin Brown, 1916. 1 — In a paper read before the 4th Indian 

 Science Congress at Bangalore in January 1917, only a brief summary 

 of which has been published, the following tentative views were 



advanced : — 



(1) The remarkable absence of such characteristic pneumato- 

 lytic minerals as tourmaline, topaz, etc., from the vein 

 association appears to prove that fluorine and boron-bearing 

 compounds, the typical mineralisers of the text books, 

 played a subordinate part as far as the formation of wolfram 

 was concerned. 



1 Coggin Brown (3), pp. 10-'-103. 



